gopls: update go.mod for v0.1.7

Change-Id: I8953ba567b7aecb664a093acd5a91370a6e1fde9
Reviewed-on: https://go-review.googlesource.com/c/tools/+/196280
Reviewed-by: Ian Cottrell <iancottrell@google.com>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
diff --git a/gopls/go.mod b/gopls/go.mod
index 45b1a67..399c801 100644
--- a/gopls/go.mod
+++ b/gopls/go.mod
@@ -2,6 +2,6 @@
 
 go 1.11
 
-require golang.org/x/tools v0.0.0-20190916172013-cb62a53de387
+require golang.org/x/tools v0.0.0-20190918214516-5a1a30219888
 
 replace golang.org/x/tools => ../